Method of manufacturing variable resistance device

ABSTRACT

A process for producing a variable resistance device by intermittently advancing a strip of electrically conductive material through a plurality of work stations. Portions of the conductive material are bent to form a plurality of guides. A substrate element having a resistance track and a conductive track formed on a first surface thereof is placed onto the conductive material, the guides maintaining the substrate element accurately positioned. Preselected ones of the guides are bent into overlapping relation with the first surface of the substrate element and are thereafter permanently affixed in position. The preselected ones of the guides form termination tabs for the terminal pins of the resistance device.

United States Patent 1191 Yungblut et al.

[ METHOD OF MANUFACTURING VARIABLE RESISTANCE DEVICE [75] Inventors: Charles W. Yungblut; Robert D.

Hill, Jr., both of Irvine, Calif.

[73] Assignee: Spectrol Electronics Corporation,

City of Industry, Calif.

[22] Filed: May 31, 1974 [21] App]. No.1 475,087

[ 1 Mar. 11, 1975 3,729,817 5/1973 De Rouen et al 29/610 Primary Examiner-C. W. Lanham Assistant ExaminerVictor A. Dipalma Attorney, Agent, or Firm-J. Raymond Curtin; Barry E. Deutsch [57] ABSTRACT A process for producing a variable resistance device by intermittently advancing a strip of electrically conductive material through a plurality of work stations. Portions of the conductive material are bent to form a plurality of guides. A substrate element having a resistance track and a conductive track formed on a first surface thereof is placed onto the conductive material, the guides maintaining the substrate element accurately positioned. Preselected ones of the guides are bent into overlapping relation with the first surface of the substrate element and are thereafter permanently affixed in position. The preselected ones of the guides form termination tabs for the terminal pins of the resistance device.

6 Claims, 5 Drawing Figures i ll MB O: V 0m 09 --O O 0 O O 0 0 Q 0 0 EE EEEEEESFSGE NM METHOD OF MANUFACTURING VARIABLE RESISTANCE DEVICE BACKGROUND OF THE INVENTION This invention relates to a method of manufacturing variable resistance devices and in particular, to a method which is readily adaptable to automatic machine production of the devices.

The utilization of variable resistance devices such as potentiometers of various sizes and configurations is widespread throughout modern society. Generally, the trend of the potentiometer manufacturing industry has been to decrease the size of the devices.

Heretofore, the basic assembly of most variable resistance devices has been accomplished via manual means. As the size of such devices has been further reduced, the ability of the assembler of the devices to rapidly and accurately assemble the parts thereof has been decreased due to the miniaturized size of the parts employed. As a consequence, the labor rate per unit manufactured has increased. In addition, uniformity of quality from one device to the next has not always been consistently obtained.

Accordingly, there has resulted a definite need in the industry to provide methods of manufacturing which are readily adaptable to automatic machine production. Examples of relevant prior art are illustrated in US. Pats. Nos. 3,574,929 and 3,729,817. However, such prior art fails to disclose the present invention.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a method of manufacturing a variable resistance device which is readily adaptable to automatic machine production.

It is a further object of the invention to decrease the cost of manufacturing a variable resistance device while increasing the quality by increasing the uniformity thereof.

It is a further object of the present invention to intermittently advance a metal strip through a plurality of work stations whereat the strip is formed or otherwise utilized in manufacturing the device.

The present invention relates to a process for producing a variable resistance device by intermittently advancing a strip of electrically conductive material through a plurality of work stations. Portions of the conductive material are bent to form a plurality of guides. A substrate having a resistance track and a conductive track formed on a first surface thereof is placed onto the advancing conductive material. The guides maintain the substrate accurately positioned relative to the material. Preselected ones of the guides are bent into overlapping relation with the first surface of the substrate. The preselected ones of the guides are then permanently affixed into the overlapping relation relative to the surface of the substrate, the preselected ones of the guides forming termination tabs for the terminal pins of the resistance device.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a plan view showing successive changes effected along an intermittently advancing conductive metal strip during the process of manufacturing a variable resistance device in accord with the procedure of the present invention;

FIG. 2 is a sectional view of the advancing strip, taken along the line II-Il of FIG. 1, showing one of the successive changes;

FIG. 3 is a sectional view of the advancing strip, taken along the line III-III of FIG. 1;

FIG. 4 is a plan view similar to FIG. 1, illustrating later stages in the manufacturing process; and

FIG. 5 is a sectional view of the resistance device after it has been completely manufactured.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the various figures of the drawings, there is illustrated the manner in which the variable resistance device may be manufactured in accordance with the present invention. In referring to the various figures, like numerals shall refer to like parts.

Referring particularly to FIG. I, there is illustrated a strip of electrically conductive material 10. Strip I0 is intermittently advanced through a plurality of work stations, to be more fully described hereinafter, at which the various processing steps involved in forming the device occur.

Strip 10 preferably is provided as a roll. The strip is unwound from the roll and advanced through the various processing stations via suitable means which engage pilot holes 12 formed in the strip. The strip, as ini-,

tially provided, includes a number of blanked out or open portions l3, l4, l5, l6, and 17.

At a first station 20, portions of the conductive strip 10 are bent or otherwise formed to provide a plurality of guide surfaces 21, 22, 23, 24, 25 and 26. Preferably, portions of the strip forming fingers l8, 19, 27 and 28 are bent upwardly at right angles to the plane of the strip, to form the guide surfaces.

At next station 30, unwanted portions of strip 10 are removed therefrom via suitable means such as a stamping process. The removal of the unneeded portions of the strip provides an open ended area 31.

The strip is advanced to station 40, whereat a sub strate 41 is loaded onto the advancing strip. The guide surfaces 21-26 formed at station 20 maintain the substrate accurately positioned relative to advancing strip 10.

Preferably, as shown in FIG. 2, the guide surfaces are bent at substantially right angles to the plane of the strip. Accordingly, surfaces 21, 22, 23 and 24 prevent any transverse movement of the substrate relative to the strip. Surfaces 25, and 26 prevent any axial movement of the substrate relative to the strip.

At station 50 preselected ones of the guide surfaces are bent into overlapping relation relative to substrate 41. Preferably, guide surfaces 21, 23 and 24 are placed in contact with the end portions of conductive track 42 formed on the surface of substrate 41. With particular reference to FIG. 3, it is observed that the selected guide surfaces are bent at substantially to contact the face of substrate 41.

At station 60, the guide surfaces are permanently affixed in their overlapping position relative to the substrate by suitable means, for example solder 61.

With the guide surfaces permanently affixed to the substrate, the axial side locators are no longer needed. Consequently, at station 70, the portion of strip 10 having the guide surfaces 25 and 26 is removed from the strip by suitable means such as a stamping die.

Referring now to FIG. 4, there is shown later stages in the manufacturing process. In the preferred embodiment, at the end of every th substrate, severing means separates the group of 10 substrates including the portion of the strip still attached thereto from the remainder of the strip. The group of 10 substrates is then brought to a processing station 80, shown in FIG. 4, whereat carrier strip 10 is preferably inverted to facilitate the remainder of the processing. At station 80, housing assembly 81 of the variable resistance device is placed about substrate 41. Portions 82 of housing assembly 81 are deformed, by suitable means such as staking to permanently affix the housing relative to the substrate.

The strip is advanced to station 90 whereat further portions of the strip is removed. As is readily observable, axially extending portions of the strip connecting transversely extending fingers 91, 92 and 93, as seen at station 80, is removed at station 90.

At station 100, the middle transversely extending finger 92 is separated from the carrier strip at point 101. At station 110, the finger is bent at right angles to the substrate. Eventually, this finger will form one of the terminals of the variable resistance device.

At station 120, the housing including the substrate, is bent or rotated at 90 relative to strip 10. At station 130, suitable material, for example an epoxy compound, is then placed above the surface of the substrate to close off the wall thereof. The epoxy is permitted to cure and thence the variable resistance device is severed from the remaining portion of the carrier strip 10. Fingers 91 and 93 form two additional terminals for the resistance device. It should be understood that it is within the scope of the present invention to eliminate the need for severing every 10th substrate and thus the process would continue on the strip in an uninterrupted manner.

Referring now to FIG. 5, there is shown a sectional view of the finished variable resistance device.

The device includes housing assembly 81 having a rotor assembly 44 rotatably received within a bore 43 of the housing. An O-ring 45 or other suitable means is employed to prevent foreign matter from entering through the space provided between rotor 44 and housing assembly 81. The rotor assembly includes a wiper or contact member 46 mounted thereon. As is known to those skilled within the art, wiper 46 is movable along the resistance track 47 of the resistance device to vary the resistance thereof as is desired.

Substrate 41 is provided in the housing assembly. As noted hereinbefore, the housing assembly is placed about the substrate at station 80 of the manufacturing process heretofore described. Before reaching station 80, rotor assembly 44 has already been inserted into its position within housing assembly 81.

The substrate is preferably formed from a nonconductive material which may be in the form ofa circular, rectangular, or square disk orwafer. In the preferred embodiment the substrate is shown as a substantially square disk. Other geometric configurations may be suitably employed.

Referring particularly to FIG. 1, substrate 41 includes conductive track 42 and resistance track 47. Both the conductive and resistance tracks are applied 6 to the substrate in a configuration desired for the particular application. In the disclosed device, the resistance material is placed on the substrate in a substantially annular or are shaped configuration. The material may be applied to the substrate by any well known methods, for example brushing, spraying, stenciling or silk screening. Those areas on the surface of the sub- 5 strate upon which it is desired not to deposit any material are masked by suitable means. Suitable resistance material may include a carbon film or a composition known to those skilled in the art as cermet."

Referring to FIG. 5, epoxy 121 is provided as noted.

heretofore at station 120 to close off the area above the substrate to permanently seal the various components of the resistance device within the housing assembly. The epoxy provides a permanent seal to prevent foreign matter from gaining entrance into the interior of the resistance device. Terminal pins 91, 92 and 93 formed in the manner heretoforediscussed extend outwardly through the epoxy to provide means for externally connecting suitable electrical elements to the resistance device.

The process heretofore described enables the resistance device to be manufactured with a minimal amount of manual labor. In particular, the carrier strip is provided as a conduit for successively advancing the components of the resistance device through the various stages of the process. The strip is also used to form a portion of the completed resistance device. In particular, the guide surfaces formed from portions of the strip, and used to accurately locate the substrate relative to the strip, are also used to form termination tabs for joining terminal pins to the conductive track. Additionally, the terminal pins are formed from the carrier strip.

While a preferred embodiment of the present invention has been described and illustrated, the invention should not be limited thereto, but may be otherwise embodied within the scope of the following claims.

We claim: 1. A process for producing a variable resistance de vice by intermittently advancing a strip of electrically conductive material through a plurality of work stations comprising the steps of:

bending portions of the conductive material to form a plurality of guides;

placing a substrate having a resistance track and a conductive track formed on a first surface thereof, onto said conductive material, said guides maintaining the substrate accurately positioned relative to said material;

bending preselected ones of said guides into overlapping relation with the first surface of the substrate; and

permanently affixing said preselected ones of said guides into said overlapping relation with the surface of said substrate, said preselected ones of said guides forming termination tabs for terminal pins of the resistance device.

2. A process for producing a variable resistance device by intermittently advancing a strip of electrically 6 conductive material through a plurality of work stations comprising the steps of:

bending portions of the conductive material at right angles to form a plurality of guide surfaces; removing portions of excess material from said conductive material;

placing a substrate having a resistance track and a conductive track formed on a first surface thereof, onto said conductive material, said guide surfaces accurately maintaining the position of said substrate in both axial and transverse directions;

bending preselected ones of said guide surfaces into overlapping relation with the first surface of the substrate;

permanently affixing said preselected ones of said guides into said overlapping relation relative to the surface of the substrate, said preselected ones of said guides thereby forming termination tabs for the terminal pins of the resistance device;

removing additional excess material from the conductive material;

placing the housing assembly of the resistance device about the substrate;

permanently affixing the housing assembly to the substrate;

removing additional excess material from the conductive material, portions of the material remaining connected to the substrate defining terminal pins for the resistance device, said terminal pins extending from the guide surface of the conductive material; and

removing the assembled device from the remaining unused portion of the conductive material.

3. A process in accordance with claim 2 wherein the housing assembly has a rotor assembly installed therein prior to its being placed about the substrate.

4. A process in accordance with claim 3 wherein the preselected ones of said guide surfaces are brought into direct contact with end portions of said conductive track.

5. A process in accordance with claim 2 wherein the preselected ones of said guide surfaces are brought into direct contact with end portions of said conductive track.

6. A process in accordance with claim 1 wherein the preselected ones of said guide surfaces are brought into direct contact with end portions of said conductive track. 

1. A process for producing a variable resistance device by intermittently advancing a strip of electrically conductive material through a plurality of work stations comprising the steps of: bending portions of the conductive material to form a plurality of guides; placing a substrate having a resistance track and a conductive track formed on a first surface thereof, onto said conductive material, said guides maintaining the substrate accurately positioned relative to said material; bending preselected ones of said guides into overlapping relation with the first surface of the substrate; and permanently affixing said preselected ones of said guides into said overlapping relation with the surface of said substrate, said preselected ones of said guides forming termination tabs for terminal pins of the resistance device.
 1. A process for producing a variable resistance device by intermittently advancing a strip of electrically conductive material through a plurality of work stations comprising the steps of: bending portions of the conductive material to form a plurality of guides; placing a substrate having a resistance track and a conductive track formed on a first surface thereof, onto said conductive material, said guides maintaining the substrate accurately positioned relative to said material; bending preselected ones of said guides into overlapping relation with the first surface of the substrate; and permanently affixing said preselected ones of said guides into said overlapping relation with the surface of said substrate, said preselected ones of said guides forming termination tabs for terminal pins of the resistance device.
 2. A process for producing a variable resistance device by intermittently advancing a strip of electrically conductive material through a plurality of work stations comprising the steps of: bending portions of the conductive material at right angles to form a plurality of guide surfaces; removing portions of excess material from said conductive material; placing a substrate having a resistance track and a conductive track formed on a first surface thereof, onto said conductive material, said guide surfaces accurately maintaining the position of said substrate in both axial and transverse directions; bending preselected ones of said guide surfaces into overlapping relation with the first surface of the substrate; permanently affixing said preselected ones of said guides into said overlapping relation relative to the surface of the substrate, said preselected ones of said guides thereby forming termination tabs for the terminal pins of the resistance device; removing additional excess material from the conductive material; placing the housing assembly of the resistance device about the substrate; permanently affixing the housing assembly to the substrate; removing additional excess material from the conductive material, portions of the material remaining connected to the substrate defining terminal pins for the resistance device, said terminal pins extending from the guide surface of the conductive material; and removing the assembled device from the remaining unused portion of the conductive material.
 3. A process in accordance with claim 2 wherein the housing assembly has a rotor assembly installed therein prior to its being placed about the substrate.
 4. A process in accordance with claim 3 wherein the preselected ones of said guide surfaces are brought into direct contact with end portions of said conductive track.
 5. A process in accordanCe with claim 2 wherein the preselected ones of said guide surfaces are brought into direct contact with end portions of said conductive track. 